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Abstract: In the present study, porcine buccal and vaginal mucosae were successfully characterised by ATR–FTIR for the first time and compared to porcine ear skin. By analysing typical bands of the spectra, the structure of proteins and the lipid matrix were elucidated. According to the body site, differences in membrane permeability were detected when analysing the CH2-stretching and -scissoring vibrations. The results indicated a higher permeability for porcine vaginal and buccal tissue compared to skin. Furthermore, the influence of a lecithin-based microemulsion on the barrier properties of the above mentioned tissues was investigated by ATR–FTIR; the results revealed structural changes in all tissues. In addition, the ATR–FTIR technique was employed to semi-quantitatively analyse compounds directly on skin. To this end, tape stripping experiments were performed with a deuterated liposomal drug delivery system containing the model drug flufenamic acid. While the amount of penetrated deuterated liposomes was determined directly on skin samples by ATR–FTIR, the drug amount was analysed by HPLC after extraction of the tape strips since higher sensitivity was achieved in this fashion. Thus, it was possible to monitor the skin penetration of drug and vehicle simultaneously. Interestingly, the results indicated an independent drug penetration after release from the liposomal carrier system. [Copyright &y& Elsevier]

The skin penetration of flufenamic acid (Fluf) and fluconazole (Fluc) from innovative natural microemulsions was investigated in tape-stripping experiments on pig ears. The formulations were based on the eudermic surfactants lecithin, sucrose laurate, alkylpolyglycoside or a mixture thereof. The quantification of the penetrated drug amounts was executed by 19F nuclear magnetic resonance (NMR) in comparison with high-performance liquid chromatography (HPLC). The data obtained by the 19F NMR method were confirmed by additional quantitative studies using HPLC. An excellent linear correlation was found for Fluf as well as for Fluc between 19F NMR and HPLC data. This work presents a strategy outlining the use of 19F NMR to selectively monitor the skin penetration routes of fluorinated compounds. Fluc penetrated generally well into the stratum corneum with the significantly highest amounts from the sucrose laurate microemulsion on the tape strips 1-5. Similarly, the highest amounts of penetrated Fluf could be observed from the formulation based on sucrose laurate. In addition, NMR self-diffusion studies were conducted and revealed a bicontinuous microstructure of the investigated microemulsions. The skin penetration results are in good agreement with the obtained 19F NMR self-diffusion coefficients of the active compounds in the microemulsion systems. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:2699-2706, 2013 [ABSTRACT FROM AUTHOR]

Background Despite the frequent use of porcine ear skin for tape-stripping experiments, the peculiarities of this skin type have not been characterised in detail yet. Thus, different techniques were employed to investigate the skin surface structure of porcine ear skin and the changes in barrier function during in vitro tape stripping. To this end, the potential of capacitance-based skin hydration imaging as a means of skin quality control was investigated for the first time. Methods The porcine ear model was characterised before and during tape stripping using transepidermal water loss ( TEWL) measurements, capacitance-based sensor imaging, attenuated total reflection Fourier transform infrared spectroscopy ( ATR- FTIR) and optical light microscopy. Results The capacitance-based sensor was found to deliver precise information about the quality of the employed skin sites before and during tape stripping. The removal of stratum corneum proteins was highly reproducible even for different porcine ear types. The mean greyscale values showed an excellent linear correlation to the corresponding TEWL values and the respective penetration depth. Optical light microscopy confirmed the presence of canyons on the surface of porcine ear skin. Conclusion The results suggest that the capacitance-based sensor is a suitable tool for skin integrity testing of porcine ear skin in vitro and for monitoring changes in skin barrier function. [ABSTRACT FROM AUTHOR]

Abstract: Porcine ear skin is frequently used as a substitute for human skin in dermatological research and is especially useful for tape stripping experiments where the penetration of active substances into the uppermost skin layers is investigated. However, certain differences between the surface properties of these skin types exist, and reports on the comparability of tape stripping data obtained in vitro using porcine ear skin and data obtained in vivo on human forearm skin are scarce. Thus, we performed comparative tape stripping experiments in which the skin penetration of curcumin and fluorescein sodium from conventional microemulsions and hydrogels was investigated. In this context, the skin penetration potential of novel semi-solid macroemulsions and fluid nanoemulsions based on sucrose stearate was evaluated as well. The removed corneocytes were quantified by NIR-densitometry using recent correlation data for human and porcine proteins. The trends observed for the skin penetration into porcine ear skin were highly representative for the in vivo situation on human skin, confirming that the porcine ear is an excellent in vitro model for tape stripping experiments. Moreover, the validity of the NIR-densitometric approach for the quantification of both human and porcine stratum corneum proteins was confirmed in this study for the first time. [Copyright &y& Elsevier]